Exhaust manifold having improved NVH characteristics

ABSTRACT

An exhaust manifold and method of manufacturing the same is provided that includes at least one tube within shells of an exhaust manifold. The tube limits fluid communication from the tube into the shells of the exhaust manifold. An inlet flange is connectable to the exhaust manifold and is attachable to a cylinder head of a combustion engine. Exhaust gases expelled from the cylinder head are transmitted into the exhaust manifold. At least a portion of the exhaust gases pass through the tube. The exhaust manifold reduces NVH and cures emission control issues.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit from U.S. Provisional Patent Application No. 60/934,376, entitled “Exhaust Manifold Having Improved NVH Characteristics,” filed on Jun. 13, 2007, which is hereby incorporated in its entirety by reference.

FIELD OF THE INVENTION

This invention generally relates to an exhaust manifold that may be incorporated into an internal combustion engine, and more particularly to an exhaust manifold having exhaust tubes within an exhaust manifold housing that may improve noise, vibration and harness characteristics of the manifold housing.

BACKGROUND

In an internal combustion engine, a cylinder head is positioned atop an engine block having cylinders (or combustion chambers) extending therethrough. Upper portions of each combustion chamber extend through the cylinder head, where the upper portion of each combustion chamber corresponds with each cylinder of the engine block. The cylinder head may also house intake valves, exhaust valves, camshaft(s), rocker arms and pushrods, and numerous other mechanisms as is known in the art.

In addition, an intake manifold and an exhaust manifold are typically coupled to the cylinder head. The intake manifold is typically located between the carburetor and the cylinder head to supply an air-fuel mixture to each combustion chamber through internal intake ports in the cylinder head. In multi-port injected engines, for example, the intake manifold contains fuel injectors that supply an air-fuel mixture to each combustion chamber.

The exhaust manifold is typically coupled to the side of the cylinder head opposite the intake manifold (i.e. the “exhaust side”). The exhaust manifold collects exhaust gases exiting from each combustion chamber through internal exhaust ports in the cylinder head. The exhaust manifold then transfers the exhaust gases to an exhaust pipe of an exhaust system. Accordingly, the exhaust manifold is coupled to the cylinder head at the exhaust ports of the cylinder head such that the exhaust manifold collects exhaust gases exiting each combustion chamber within the manifold housing and transfers the exhaust gases to the exhaust pipe.

Traditionally, exhaust manifolds have been made from conventional cast iron for strength and durability. However, these manifolds are heavy, cumbersome, and therefore detract from the fuel efficiency of the vehicle. In addition, the cast iron manifolds are difficult to manufacture into compact shapes and other distinct shapes as may be required by the underhood packaging constraints of modern vehicles.

One solution to the problems presented by the traditional cast iron manifolds is to fabricate the exhaust manifolds from thin sheet metal, which is lightweight and more easily complies with underhood packaging constraints. However, these sheet metal manifolds present several disadvantages. In particular, since the sheet metal manifolds are thin and lighter in weight, the sheet metal manifolds provide noise, vibration, and harshness (“NVH”) problems. For example, the NVH problems present objectionable noise and vibration from the exhaust pulses. Specifically, the NVH passes from the manifold housing into the engine compartment, and ultimately onto the passenger compartment. Furthermore, the sharing of exhaust pulses among cylinders via the exhaust manifold (i.e. “cross-talk”) may compound the NVH problems and may result in further objectionable noise and vibration. The NVH transmitted and experienced by the passengers is bothersome and undesirable.

Consequently, there exists a significant need for an exhaust manifold that is durable, lightweight and capable of reducing NVH. In addition, a need exists for an exhaust manifold capable of being tuned to reduce and/or to dampen noise and vibrations of an exhaust system, such as noise and vibrations due to exhaust pulses from the internal combustion process.

SUMMARY OF THE INVENTION

An exhaust manifold assembly is provided. The exhaust manifold assembly may consist of an upper half shell secured to a lower half shell to form a housing. The upper half shell and/or the lower half shell may have one or more tubes extending within the interior of the housing. An inlet flange and an outlet flange may be attached to one of the shells. The inlet flange may be attached to a cylinder head to receive exhaust gases from the cylinder head. The exhaust gases may be received by the one or more tubes. Advantageously, the improved exhaust manifold assembly may reduce NVH.

BRIEF DESCRIPTION OF THE DRAWING

Objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustration, wherein:

FIG. 1 is a cross-sectional view of an embodiment of an exhaust manifold in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, an exhaust manifold 10 is illustrated. The manifold 10 may include a lower half shell 20 and an upper half shell (not shown). The lower half shell 20 and the upper half shell may be integrally formed, attached, such as by welding or fastening, or otherwise joined together. The upper half shell and the lower half shell 20 may be joined to define a housing 25.

The housing 25 may be defined between the upper half shell and the lower half shell 20. The housing 25 may have an outlet flange 40 providing fluid communication between an interior 15 of the housing 25 and an exterior 16 of the housing 25. The outlet flange 40 may have an opening 55 permitting fluid communication between the remainder of the exhaust system and the housing 25. The outlet flange 40 may be sized and shaped for attachment to a remaining portion of the exhaust system (e.g. exhaust piping, turbocharger, etc.). The outlet flange 40 may be connected to the housing 25, such as to the upper half shell and/or the lower half shell 20. For example, the outlet flange 40 may be coupled to a first side 36 of the housing 25. The outlet flange 40 may be integrally formed with the lower half shell 20 and/or the upper half shell. Alternatively, the outlet flange 40 may be a separate piece which is secured to one of or both of the half shells via, for example fasteners, a press-fit, welding, brazing, an adhesive or the like. In an embodiment, the upper half shell may have a portion of the outlet flange 40, and the lower half shell 20 may have a corresponding portion of the outlet flange 40 such that joining the upper half shell and the lower half shell 20 results in formation of the outlet flange 40.

An inlet flange 30 may be connected to the housing 25. For example, the inlet flange 30 may be secured to one of or both of the upper half shell and the lower half shell 20 by way of fasteners, a press-fit, welding, brazing, an adhesive or in another manner that will be appreciated by a person of ordinary skill in the art. In an embodiment, the inlet flange 30 may be integrally formed with the upper half shell or the lower half shell 20 or may be separately connected to the housing 25. The inlet flange 30 may be formed by the joining of the upper shell and the lower half shell 20. For example the upper half shell may have a portion of the inlet flange 30 and the lower half shell 20 may have a corresponding portion of the inlet flange 30 such that joining the upper half shell and the lower half shell 20 results in formation of the inlet flange 30.

The inlet flange 30 may be positioned adjacent to or at a second side 35 of the housing 25, which may be adjacent to the manifold 10. The second side 35 of the housing 25 may be opposite to the first side 36 of the housing 25 where the outlet flange 40 may be attached. In use, the inlet flange 20 may be secured to the exhaust side of a cylinder head, for example. The inlet flange 30 may comprise one or more openings 50 (or apertures). Each of the openings 50 may provide fluid communication between the interior 15 of the housing 25 and the exterior 16 of the housing 25. The openings 50 may transmit exhaust gases from the cylinder head into the housing 25. In an embodiment, the number of the openings 50 may correspond to the number of the exhaust ports in the cylinder head.

Alternatively, the number of the openings 50 may be greater than or less than the number of the exhaust ports in the cylinder head. In an embodiment, the inlet flange 30 may have at least one of the openings 50 receiving exhaust gases from two or more of the exhaust ports of the cylinder head. In another embodiment, the inlet flange 30 may have at least two of the openings 50 receiving exhaust gases from one of the exhaust ports of the cylinder head. A person of ordinary skill in the art should not be deemed as limited to any number of the openings 50. The inlet flange 30 may have any number of the openings 50 and may attach to the cylinder head in any manner capable of transmitting exhaust gases from a cylinder head to the interior of the housing 25.

One or more tubes (or pipes) 60 may be positioned within the housing 25. The one or more tubes 60 are hereinafter referred to as “the tubes 60” for simplicity and clarity purposes and not to limit the present invention to requiring two or more of the tubes 60. It is clearly contemplated that “the tubes 60” may consist of a single tube. The tubes 60 may be any shape capable of transmitting fluids, such as exhaust gases therethrough. For example, the tubes 60 may be cylindrical pipes for transmitting fluids through the housing 25. The tubes 60 may be separated from one another such that NVH, such as noise and vibrations from one of the tubes 60 is not transmitted to another one of the tubes 60. In addition, the tubes 60 may absorb the NVH and dampen the NVH felt or otherwise received by the upper half shell and the lower half shell 20.

Each of the tubes 60 may be attached to the inlet flange 30, the outlet flange 40, and/or the housing 25. The tubes 60 may be secured within the housing 25 via fasteners, a press-fit, welding, brazing, an adhesive or the like. The tubes 60 may be attached to or connected to the housing 25 to support the tubes, for example. Alternatively, the tubes 60 may simply rest on any suitable surface within the housing 25 or rest on mesh rings or pads 70 positioned between each tube 60 and any suitable surface within the housing 25. The pads 70 may be attached to the upper half shell or the lower half shell 20 to support the tubes 60.

In an embodiment, the tubes 60 may be attached at the openings 50 of the inlet flange 30. For example, the tubes 60 may extend from the inlet flange 30 to the outlet flange 40. In such an embodiment, the tubes 60 may be attached to the inlet flange 30 and the outlet flange 40.

The tubes 60 may be die cast or formed by other methods and processes known to those skilled in the art. The upper half shell and the lower half shell 20 may be die cast or overmolded around the tubes 60. In such an embodiment, the tubes 60 may be positioned within a mold at predetermined angles and lengths. The upper half shell and/or the lower half shell 20 may be cast with the tubes 60. In such an embodiment, the tubes 60 may be integrally formed with the upper half shell and/or the lower half shell 20.

In another embodiment, each of the tubes 60 is secured to the inlet flange 30 and terminates within the housing 25, without attachment to the outlet flange 40. For example, the tubes 60 may terminate a distance from the outlet flange 40. In such an example, the distance may be sufficient for the exhaust gases to mix within the interior 15 of the housing 25 prior to exiting at the outlet flange 40. Termination of the tubes 60 short of the opening 55 of the outlet flange 40 may permit the exhaust gases exiting the tubes 60 to mix within the housing 25 prior to passing through the opening 55 and onto other components of the exhaust assembly, such as a HEGO sensor and/or catalytic converter. Properly mixing the exhaust gases within the housing 25 prior to exiting at the outlet flange 40 may reduce inaccurate emission readings and limit problems with emissions controls.

In yet another embodiment, the tubes 60 may be attached to the outlet flange 40 without attachment to the inlet flange 30. For example, the tubes 60 may extend from the outlet flange 40 towards the inlet flange 30 and terminate a distance from the inlet flange 30. The tubes 60 may extend within the housing 25 without attachment to the inlet flange 30 and the outlet flange 40 in another embodiment of the present invention. In such an embodiment, the tubes 60 may terminate a first distance from the inlet flange 30 and a second distance from the outlet flange 40. The first distance may be substantially similar to or different from the second distance.

The tubes 60 may combine embodiments herein described. For example, one of the tubes 60 may be attached to the inlet flange 30, and another one of the tubes 60 may not be attached to the inlet flange 30 and the outlet flange 40. To this end, the tubes 60 may have different lengths and dimensions.

The tubes 60 may have a wall structure 62 for preventing or at least limiting fluid communication from an interior 64 of the tubes 60 to the interior 15 of the housing 25. To this end, the wall structure 62 of the tubes 60 may be metallic, plastic, or other material, preferably capable of transmitting relatively high temperature fluids therethrough. The wall structure 62 may have one or more layers separating an interior 64 of the tubes 60 from the interior 15 of the housing 25.

In an embodiment, the wall structure 62 may have one or more apertures or perforations (not shown) for permitting fluid communication from the interior 64 of the tubes 60 into the interior 15 of the housing 25. The perforations (or apertures) may provide limited fluid communication to the interior 15 of the housing 25 such that a portion of the exhaust gases exit the tubes 60 into the interior 15 of the housing 25.

The tubes 60 may be arranged such that exhaust gases flow through each of the tubes 60 towards the opening 55 of the outlet flange 40. Advantageously, the tubes 60 may capture exhaust pulses exiting the cylinders thereby insulating the outer shell of manifold 10 from sound waves associated with these exhaust pulses leading to NVH improvement of the manifold 10 and vehicle as a whole. Furthermore, the tubes 60 may allow more flow separation of exhaust gases exiting each cylinder thereby significantly reducing, or even eliminating, NVH problems from cross-talk among cylinders. Additionally, the tubes 60 may also absorb thermal energy from the exhaust gases thereby reducing thermal energy transferred to and absorbed by other components of the manifold 10 thus improving overall durability of the manifold 10.

In addition, the tubes 60 may be configured to provide additional NVH benefits, such as damping noise and vibration within the manifold 10 and/or tuning the manifold 10 to enhance the sound quality of the exhaust system and the entire vehicle. For example, some degree of tuning and/or damping may be possible by the appropriate selection of various physical characteristics of each tube 60, such as length, cross-sectional shape, endform, wall structure, tube wall thickness, perforations or apertures in the wall structure of the tubes 60, material composition, or the like.

Although the preferred embodiment of the present invention has been illustrated in the accompanying drawing and described in the foregoing detailed description, it is to be understood that the present invention is not to be limited to just the preferred embodiment disclosed, but that the invention described herein is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the claims hereafter. 

1. An exhaust manifold comprising: an upper half shell; a lower half shell secured to the upper half shell to define a housing; and a tube positioned within an interior of the housing, the tube having a wall structure to substantially limit fluid communication between an interior of the tube and the interior of the housing.
 2. The exhaust manifold of claim 1 further comprising: an inlet flange attached to one of the lower half shell or the upper half shell, the inlet flange attachable to a cylinder head of a combustion engine.
 3. The exhaust manifold of claim 2 wherein the tube is attached to the inlet flange.
 4. The exhaust manifold of claim 3 further comprising: an opening formed in the inlet flange, the openings providing fluid communication between an exterior of the housing and the interior of the housing.
 5. The exhaust manifold of claim 3 further comprising: an outlet flange attached to one of the lower half shell or the upper half shell, the outlet flange attached at an opposite side of the housing from the inlet flange.
 6. The exhaust manifold of claim 5 wherein the tube extends from the inlet flange and terminates prior to the outlet flange.
 7. The exhaust manifold of claim 6 wherein the tube is connected to the inlet flange at the opening of the inlet flange.
 8. The exhaust manifold of claim 5 wherein the tube is connected to the inlet flange and the outlet flange.
 9. The exhaust manifold of claim 5 wherein the tube extends from the outlet flange and terminates within the housing without connection to the inlet flange.
 10. The exhaust manifold of claim 5 wherein the tube extends within the housing and terminates a first distance from the inlet flange and a second distance from the outlet flange.
 11. An exhaust manifold comprising: a housing including an upper half shell and a lower half shell, the housing attachable to a cylinder head of an internal combustion engine; and a plurality of tubes positioned at least partially within the housing, the tubes having a wall structure to limit fluid communication between an interior of the tubes and the housing.
 12. The exhaust manifold of claim 11 further comprising: an inlet flange connected to the housing and securable to combustion chambers of an internal combustion engine.
 13. The exhaust manifold of claim 12 wherein the inlet flange has a plurality of openings, and further wherein the tubes are equal in number to the openings in the flange.
 14. The exhaust manifold of claim 12 wherein at least one of the plurality of tubes is connected to the inlet flange and extends within the housing.
 15. The exhaust manifold of claim 12 wherein the plurality of tubes are within the housing without attachment to the inlet flange.
 16. The exhaust manifold of claim 12 further comprising: an outlet flange connected to the housing, the outlet flange connected at an opposite end of the housing from the inlet flange.
 17. The exhaust manifold of claim 16 wherein at least one of the plurality of tubes extends from the inlet flange and terminates a distance from the outlet flange without attachment to the outlet flange.
 18. A method for manufacturing an exhaust manifold assembly comprising: forming a first half shell; positioning a plurality of tubes within the first half shell; connecting the first half shell to a second half shell to form a housing having an interior defined between the first half shell and the second half shell, the plurality of tubes positioned within the interior of the housing, wherein the plurality of tubes have a wall structure to limit fluid communication from the plurality of tubes into the housing along the length of each of the plurality of tubes; connecting at least one of the shells to an inlet flange securable to a cylinder head of an engine; and securing at least one of the tubes of the plurality of tubes to the inlet flange.
 19. The method of claim 18 wherein the first half shell and the second half shell are molded over the plurality of tubes.
 20. The method of claim 18 further comprising: connecting an outlet flange to one of the shells opposite the inlet flange, wherein at least one of the tubes terminates without attachment to the outlet flange.
 21. The exhaust manifold of claim 1 wherein the tube has one or more apertures providing fluid communication between the interior of the housing and the interior of the tube. 